It certainly was junk if it didn't even have any status display.
The first two had analog ammeters. Which always indicated zero.
The second two has status LEDs. Connected to the 1.8 volt battery, "charging" was off and "charged" was lit.
A good
charger must be able to start from zilch. Interestingly, I found out
>that many designers of SMPS do not have foldback limit, they just error.
>Maybe they don't know how to do that anymore these days.
There's no reason for a switcher to fold back. It can just current limit, cool and comfortable. Most switchers seem to do that.
On a sunny day (Mon, 28 Sep 2009 19:42:11 -0700) it happened John Larkin wrote in :
It would have been interesting to measure the voltage while it was connected. It perhaps just applied 14 V and did see no current. Voltage OK, no current = battery charged. How many [k]V do you think would be reasonable to have it try before detecting a current? That would require a multi sequence startup. First apply high voltage with low current limit to see if any mA flows. If not -> kaput -> exit. Then normal voltage with normal current limit.
A bit unreasonable to expect all that from a simple charger.
1.84 volts, charger connected or not. Zero current between charger and battery.
a current?
Why doesn't it apply a current-limited voltage and, well, charge the battery? It is a battery charger, after all.
A simple charger, like the old transformer-rectifier types, or any normal switching regulator, would dump current into a dead battery. These new ones are deliberately programmed to not.
Don't lead acid batteries charge at "constant voltage"?
That is, it is traditionally safe to apply a constant e.g. 14V to a good "12V" battery, and the charging will be self-limiting. When it's full, the current drops to a safe minimal value.
But if you had a battery where 5 out of 6 cells are shorted out, then you are relying on that one good cell to terminate the charge safely. But it never will, your constant-current charger will keep on pushing maximum current through it, electrolysing the fluid. All that deadly explosive hydrogen gas and lethal sulphuric acid... A lawsuit waiting to happen...
On a sunny day (Tue, 29 Sep 2009 08:07:15 -0700) it happened John Larkin wrote in :
Yes, there is a problem. I was reading about those air speed sensors in the Airbus planes. If one fails, and the computer sees 2 vastly different airspeeds, then the computers says 'goodbye' and stops controlling the plane.
I think you get into a situation where you ask not 'How do I fly in this situation', but: 'What does the computer think?' Or what does the computer mean by what it does? That did lead to some terrible accidents already. And I am sure as automation increases we will see more. For those pilots the computer is their ears and eyes, and it is like a simulated reality.
But can it be avoided? Everything is getting remote controlled, microprocessor controlled. It started with digital watches, just find out how to set the time or an alarm. Then it was VCRs, many people had the clock still flash 00:00 after years...
It will go to brain implants, artificial limbs, you may start hitting somebody because the software thinks it is under attack... when that ball is thrown at you...
Human brain is a complicated thing. There was the pilot some time ago who, after takeoff, shut down the engine. Confused he was...
The question is then: Will it get better or worse, with all those machines? I think it will get better, but strange things will keep happening,
We will probably learn to depend more and more on the software's judgement. You cannot be an expert in everything. And indeed industry will use this to make some extra profit (like with chipped ink cartridges), but others will provide solutions for that too. The charger manufacturer probably has no interest to sell new batteries.
The old TVs had a vertical hold knob, the later ones had automatic sync... But often did not sync to a PAL system if it was an NTSC set etc..
Maybe you could have kick started the charge by parallelling a 9 V battery for a second.... Those who understand what is happening will find a way around the problems.
And, those computer diagnostics will enter the medical field too, you may be pronounced dead, while all you needed was some air.. LOL
You could, but it's more common to connect them to a power supply that has current and voltage limiting. The old dumb chargers were just a high leakage inductance transformer and a rectifier, very sloppy voltage and current limiting, and they worked fine. It was prudent to remove them once the battery was charged, so's not to boil out all the water in the battery.
The cells weren't "shorted out", they were discharged. The fix is to charge them. I have no idea of how you define "terminate the charge safely." Personally, I'd terminate the charge when the battery is charged.
But it never will, your constant-current charger will keep on
Please explain the chemistry of that. It sounds like no batteries can be charged, ever.
All that
Transformer-rectifier chargers have been used since the days of tungar bulbs. They somehow didn't have the problems you describe. I guess applying enough microprocessors and lawyers will stop most anything from working.
Anyone with half a brain would replace a LA battery that showed 1.8V, particularly when it's your daughter's car.
But your always right, even when you're AlwaysWrong ;-) ...Jim Thompson
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*Your* battery was (let us assume), but - playing devils advocate - it might be that this is in general a sign of a failed battery, not simply a discharged one.
No idea really... I seem to recall something about overcharging liberating hydrogen and oxygen? The excess energy has to go somewhere, right?
Wikipedia agrees with me, so there!
"overcharging with high charging voltages will generate oxygen and hydrogen gas by electrolysis of water, forming an explosive mix."
'Fraid so.
(In case it is not clear I do actually agree with you - I would be pretty pissed off with a "charger" that refused to even *try* to charge a flat battery, faulty or not.)
There's an easy way to find out: recharge it and see what happens.
1.2 amps from a Lascar bench supply, overnight, is hardly overcharging. Contrary to stated theory, the car works fine now.
I guess several of the posters here, if they left their lights on and killed their battery, will always have their car towed and the battery replaced. They have no need for jumper cables, and are happy buying chargers that only charge batteries that don't need to be charged.
Soon after you turn off the lights, it should "float" to around 13.2V (no load). ...Jim Thompson
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| James E.Thompson, P.E. | mens |
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For reasons that elude me the more modern switcher chips (beyond the slow TL494 which properly provides two comparators) never offer current limit or a 2nd FB node. I usually roach that on with some discretes and stuff. If you don't then, depending on architecture, it tries to dump x watts into a load. If the load is near zero volts that means xxx amps and ... *PHUT*
I guess this is why chips like the LT3757 have a 1:5 foldback. It's inherent, you can't easily change it.
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Yeah, but: Can your PIC do 500kHz, provide clean current mode control of the inductor and blank out the first 200nsec of the MOSFET gate drive spike at the current sense node? That's kind of the state of the art these days :-)
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On a sunny day (Tue, 29 Sep 2009 12:50:58 -0700) it happened Joerg wrote in :
OK, but can your 'state of the art' chip do: Programmable frequency of 19.6, 39.6, 76.9, and 153 kHz AND Drive a LCD display. Have 4 or more 10 bit analog inputs. Processor core inside. FLASH memory inside. EEPROM inside. Reference dividers inside. Available in DIL so humans can see it. Directly drive a logic level MOSFET. Internal oscillator. Able to replace plenty of other stuff in your circuit because of programmability. Work on 2.5 to 5 V. Have serial communication. Remotely adjustable current and voltage via RS232. For the price of a PIC. Available from every electronics shop in the universe.
Doesn't need any of that. Just like my car doesn't have too much in electronics, on purpose :-)
Yes.
No, MSOP10. But I've got a microscope ...
It drives a standard level FET to 10V, which is a requirement in most of my apps. Try to get a logic level FET at 200V+.
Ahm, can your PIC swing 2500pF in around 10nsec? If it can't go from zero to at least 7V in less than 30nsec you'd hear a loud pop and a smell would waft through the air.
Yep.
programmability.
Not needed.
Yes. But can yours work at 40V?
No need. It's set and forget.
From regular distributors.
Oh, minor detail, and does you PIC come in rad hard? Anyhow, without precise current mode control most of my switcher designs wouldn't work at all or result in a loud bang.
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On a sunny day (Tue, 29 Sep 2009 14:58:38 -0700) it happened Joerg wrote in :
Yea, but for some application this is really nice.
formatting link
That link makes a nice bench power supply actually, digital readout, adjustable current limit and voltage, just the thing to charge a car battery :-) And you can program charge curves with timing for any battery.
Oh, but I have got a microscope too:-) up to 1200x with zoom. But useless for electronics.
Maybe in your application, but no pops here. I have shown you the math for the PIC solution some time ago, check memory.
If I need to order from the US here, it is already too expensive. Just the posting, and then the VAT import duty.
Why? I have no space shuttle ;-) And I would not dish out a million to fly on the ISS, and not a 100,000 to fly with Virgin to the 'edge of space'. And Borsele (nuclear plant) is far enough away from here. And the remaining Tjernobyl radiation is too weak to make a difference. And, to use your own arguments against you, is it not nice to have that remote control option if the thing has to work in a dangerous environment? Intercase for data logging is very very very nice to have.
Well, I very rarely experience bangs, if so it is because of new years fireworks.
I've always hoped uC would get some basic necessities to make a real PWM supply. Such as a programmable fixed width blanker in front of one comparator and, ideally, a HV section that can drive one or more port pins to at least 10V (supplied externally).
I use the Veho "toy scope". Very useful, decent working distance, 20x, just about right for tiny SMT stuff.
Yeah, but math doesn't miraculously pull a logic level FET out of a hat for my apps. Not even if a black cat crosses the road.
Yes, I painfully remember that, have lived in Europe myself. But my career started with a US company so we had a nice regular shipping channel.
Well, my stuff sometimes has to perform at higher altitudes. Remote control isn't useful, if it fails then not so nice things will already have happened. It's like spilled milk.
fireworks.
That's because your switchers are probably fairly small or you can afford to oversize your inductors. If your SMPS is >100W, the inductor must be small and the whole thing has to be very fault tolerant you either have current mode control or you cannot do it, usually.
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